1) If you dont fold the flop you have to fold the turn. I doubt his turn bet is ever a bluff with that much left behind and flop raise. He looks like he wants to get it allin so dont.

2) After seeing what he showed down after raising the first hand im never folding here. Its a choice between call and push any river or just push turn. He probably calls more on a blank river BUT there are plenty of scarecards that can come if he has something like 99 or TT. I probably think for a little while and then push turn. If he has Q4 then meh.

3) Ugh thats a horrible river. I personally make the turn raise bigger since you said he calls with alot. I probably make it $30-35. A $35 tun raise would make the river an instacall with the money behind.
As played you still have to call but you can expect to lose quite often.

4) 80 hands is nowhere near enough to come close to judging a steal %. Hes on the button 13 times in 80 hands. At a tightish table at least half of those wont be folded to him so its like trying to judge someones PFR percentage after 7 hands. If I dont know someone I just give them the benifit of the doubt with marginal hands out of position. I like how you played it postflop. Turn is check/fold for me.

5) Good.